During intramedullary nailing (IM) surgery it is of importance (especially in a freehand locking screw insertion procedure through large soft tissue coverage) to firmly fix the locking screw to the screw driver to avoid dropping and mis-angulating the locking screw. Present solutions are self-holding screw drivers which suffer from insufficient holding forces and susceptibility to deflexion caused by bending moment.
The screw head of the present invention offers a conical or spherical shape with an integrated external multiple, preferably triple thread (preferably a round thread and left-handed thread) which eases the adaptation of an external sleeve with internal thread. The external sleeve is guided/axially constrained by the screw driver shaft creating firm connection between sleeve and screw. Due to the conical/spherical design the outer diameter of the assembled screw head and sleeve construct does not exceed the maximum outer diameter of screw head and can be used through existing tissue protection sleeve systems. The transmission of the required torque remains utilizing the internal hex of the screw solely.
Compared to the already existing solutions the design of the present invention offers a more rigid connection under all loading conditions.